The present disclosure relates to a vacuum transfer apparatus that transfers an uneven pattern on a disk substrate with a stamper in a vacuum space, and a vacuum transfer method.
In a manufacturing procedure of optical disks, an uneven pattern such as a pit pattern or a groove pattern formed on a stamper is transferred by pressing the stamper to a photoreactive resin layer spread on a disk substrate, and curing the photoreactive resin layer.
Japanese Unexamined Patent Application Publication Nos. 2004-303385, 2005-310247, and 2006-351103 disclose a technique of transferring a pit pattern on a disk substrate with a stamper, and a technique of transferring a pit pattern in a vacuum space.
To transfer an uneven pattern, such as a pit and a land, or a groove, on a disk substrate with a stamper, the following process is typically performed. First, uncured UV-curable resin is spread on a disk substrate by spin coating.
Then, a stamper having an uneven pattern is pressed to a layer of the UV-curable resin. In this state, UV irradiation is performed, thereby curing the layer of the UV-curable resin. After the UV-curable resin is cured, the stamper is removed from the disk substrate.
Herein, in the case of transferring the uneven pattern as described above, air bubbles may be generated in the resin layer or dusts may enter the resin layer when the stamper is pressed to the layer of the uncured UV-curable resin. This may adversely affect the shape of a fine uneven pattern, and finally affect the quality of a disk reproduction signal. That is, the quality of an optical disk to be manufactured may be degraded.
To prevent air bubbles and the like from being generated, the above-described transfer process is processed in a vacuum space with a vacuum transfer apparatus.
In a vacuum transfer apparatus of a related art, a disk substrate with a layer of uncured UV-curable resin applied is conveyed to a vacuum transfer unit in which a single stamper is provided, and the stamper is pressed to the disk substrate in vacuum so as to transfer an uneven pattern. Subsequently, the substrate together with the stamper is conveyed to an UV irradiation device, the layer of the UV-curable resin is cured with ultraviolet (UV), and after the UV-curable resin is cured, the disk substrate is removed from the stamper.
Unfortunately, in such a vacuum transfer process, a manufacturing time for a single disk (transfer process time) may be increased, thereby degrading the efficiency of the optical disk production.
At the time when the disk substrate is conveyed to the vacuum transfer apparatus, the internal space of the vacuum transfer apparatus is opened to air. After the disk substrate is conveyed thereinto, the internal space is sealed, vacuuming is started, and thus, a vacuum space is created. Vacuuming is performed, for example, with a vacuum pump. Even if a vacuum pump has a high exhaust performance, increasing the degree of vacuum to a high vacuum may rapidly degrade the exhaust performance, and hence, a time is necessary for obtaining a desired degree of vacuum.
That is, relatively time-consuming vacuuming has to be performed every time when a single disk substrate is processed; resulting in that a process time for a single disk substrate may be increased.
In addition, the internal space has to be opened to air every time when a disk substrate is conveyed to or from the vacuum transfer apparatus. This may cause dusts in a peripheral area to enter the vacuum transfer apparatus.
In order to decrease the manufacturing time for a single disk substrate in the process with the vacuum transfer apparatus, it is necessary to prepare a plurality of stampers and a plurality of vacuum transfer apparatuses, so that equivalent operations are performed in a plurality of parallel lines.
However, equipment for the parallel lines may become large, thereby seriously increasing the installation cost of the production line. Further, extremely strict quality control is necessary for a stamper so as to accurately transfer an uneven pattern. If equivalent stampers are used in a plurality of lines, the quality control of these stampers may be seriously troublesome work. Thus, the large-scale lines do not provide a desired efficiency.
Therefore, it is desired to decrease a time for a vacuum transfer process, with a reduced number of stampers (desirably, a single stamper). Accordingly, it is desirable to provide a vacuum transfer apparatus capable of decreasing a time for a vacuum transfer process, and a vacuum transfer method.